Mutations that drive cancer lurk in healthy skin

Changes not so rare — nor a sign of imminent tumor growth

EYE-OPENER Normal skin is a patchwork of cells, many of which carry cancer-driving mutations, a new study finds. In a representation of normal skin, colors indicate the mutated genes and circles reflect the size of skin patches from healthy eyelids carrying the mutation.

I. Martincorena et al/Science 2015, I. Martincorena

By late middle age, about a quarter of skin cells carry cancer-driving mutations caused by exposure to sunlight — and it’s perfectly normal.

Researchers had previously thought that the types of mutations that fuel tumor growth were rare and happened just before a cell becomes cancerous. But a study of the eyelids of four people who don’t have cancer reveals that such mutations “are staggeringly common in normal skin,” says Philip Jones, a clinical scientist at the University of Cambridge.

Jones and his colleagues collected 234 skin samples from four people ages 55 to 73 who had plastic surgery to correct droopy eyelids. DNA sequencing showed that about 20 percent of the skin cells had mutations in the NOTCH1 gene, the team reports in the May 22 Science. When mutated, that gene is a driving force in some cancers, including skin cancers called squamous

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